Observations

Description

Valves are elliptical to linear-elliptical. The raphe valve has a linear axial area and a small transversely elongated central area formed by one to three shortened striae on each side. The raphe is straight, without terminal fissures. The central and terminal raphe ends are slightly expanded externally. The central raphe ends curve toward opposite sides internally. The rapheless valve has a linear-lanceolate or narrowly rhomboid axial area, and a small transversely elongated central area. Striae are radiate on both valves, 27-31 in 10 µm, interrupted at the valve margin. One row of areolae is present on the mantle of both valves. External openings of the areolae on the raphe valve are large, square or rectangular, occasionally elongated. Such openings on the rapheless valve are usually small, circular to silt-like. Internal openings of the areolae on the faces of both valves are square, on the mantle they are elliptical.

Original Description

Original Description

Valve oval with rounded ends about 7 μ long and 3 μ wide. Raphe valve with straight delicate raphe and approximate central pores, longitudinal space narrow lanceolate, central space wanting, striae radiate throughout about 33 in 10 μ the central one on each side being curtailed. Rapheless valve with lanceolate pseudo-raphe and no central space, striae less radiate than those of the complementary valve about 30 in 10 μ.

Original Images

Cite This Page: Potapova, M. (2010). Psammothidium curtissimum. In Diatoms of the United States. Retrieved August 02, 2015, from http://westerndiatoms.colorado.edu/taxa/species/psammothidium_curtissimum

Valves are elliptical to linear-elliptical. Valves very small, less than 10 μm in length. Both valves have small transversely elongated central areas. The raphe is straight, without terminal fissures. Striae are radiate on both valves, 27-31 in 10 µm.

Compare

Psammothidium curtissiumum differs from P. subatomoides by smaller size (except the smallest specimens of P. subatomoides), by very small central areas on both valves, and by generally lower striae density.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)

Autecology Discussion

Habits

Size Range

11-100 µm3 (ie Achnanthidium)

Motility

slightly motile (e.g. Cocconeis)

Attachment

prostrate (e.g. mucilage pad)

Habitat

benthic

Colony

solitary

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Psammothidium curtissimum

Distribution

The distribution map represents the relative abundance of this Psammothidium curtissimum in the western EMAP study. Relative abundance is a measure of the proportion of cells of this species based on a "fixed count" of 300 total diatom cells counted and identified. Each of the western EMAP sample sites is shown, either with a black dot for sites where Psammothidium curtissimum was not recorded, or with a red circle indicating the relative abundance of Psammothidium curtissimum.

Note that the size of the proportional symbols varies between species to help show both abundant and rare species.

Scale for the map to the left

EMAP Response Plots

Psammothidium curtissimum

Responses

The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Psammothidium curtissimum from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)STRAHLER = distribution plot of the Strahler Stream Order SLOPE = stream reach gradient (degrees)W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.PHSTVL = pH measured in a sealed syringe sample (pH units)log_COND = log concentration of specific conductivity (µS/cm)log_PTL = log concentration of total phosphorus (µg/L)log_NO3 = log concentration of nitrate (µeq/L)log_DOC = log concentration of dissolved organic carbon (mg/L)log_SIO2 = log concentration of silicon (mg/L)log_NA = log concentration of sodium (µeq/L)log_HCO3 = log concentration of the bicarbonate ion (µeq/L)EMBED = percent of the stream substrate that is embedded by sand and fine sedimentlog_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.